THE latest sex tapes confirm it&colon; size doesn’t matter – so long as you’re sneaky. Smaller male New Zealand giraffe weevils use their diminutiveness to their advantage to mate with females under the noses of their larger peers.

The bizarre-looking male giraffe weevil (Lasiorhynchus barbicornis) uses its enormous snout, or rostrum – which can make up over half its body length – to joust with other males and win mating rights. But some males have snouts just one-sixth the length of those of their most well-endowed peers.

Small males don’t let this disadvantage stand in their way, though, says Christina Painting at the University of Auckland, New Zealand. She monitored the private lives of 79 weevils and found that small males with short snouts instead use sly sexual behaviour to mate. Some would hide under a female while she copulated with a large male, ready to jump in should the larger male get distracted by a rival. Others would slowly slide unnoticed between a copulating pair and take over from the larger male.

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“It’s very hard to explain how something as insane as a long rostrum has evolved if there’s no difference in mating success across size classes,” says Painting. “We imagine the story is bigger than what we’ve revealed so far.”

This article appeared in print under the headline “Sometimes it pays to be the lesser of two weevils”

IT’S one in the eye for a “uniquely” human trait. Chimpanzees may share our ability to empathise with other individuals by involuntarily matching their pupil size. The signalling may reinforce social bonds.

Pupils constrict in response to an unfamiliar target, and then adjust and dilate. In humans, our pupils dilate more rapidly when we interact with a human whose pupils are also dilating. Our pupils dilate more slowly if the second human’s pupils are constricting.

Now Mariska Kret at the University of Amsterdam in the Netherlands and her colleagues have shown that the same thing happens in chimps. The team showed chimp and human subjects images of chimp and human pupils either dilating or constricting, while monitoring the subjects’ pupil size with a camera. Humans and chimps both involuntarily altered the rate of pupil dilation in response to the different images – although the effect was more subtle in chimps.

The study also showed that humans don’t adjust their pupils to match chimpanzee pupils, and vice versa (PLoS One, doi.org/vbr). “The fact pupil mimicry is stronger within species suggests it has a social function,” says Kret. “It may be a signal of trust and empathy.”

This article appeared in print under the headline “Chimps mimic pupil size in show of trust”

IT COULD be the ultimate stress ball for spies. An invisible ink creates secret messages on bendy plastic that are only revealed when you give it a squeeze.

Jianping Ge of the East China Normal University in Shanghai and his colleagues embedded an array of silica crystals in a plastic gel. The crystals reflect light at a certain wavelength depending on their spacing, so the relaxed gel appears green, but squeezing or stretching it turns it blue or red.

The team then coated the surface with another gel, and put a cut-out of a secret image on top. They shone ultraviolet light on the set-up, which linked the two gels around the cut-out. Once the cut-out was removed, its silhouette only appeared when the gels were squeezed (Advanced Functional Materials, doi.org/f2tmtp).

Ge says the technique could protect against counterfeit goods in the form of “anti-fake labels”.

This article appeared in print under the headline “Stretchy plastics hide secret images”

FAMOUS for smoothing wrinkles, botox could help fight stomach cancer too.

Stomach cancer is hard to treat because gastric tumours don’t always respond to chemotherapy. As nerve signalling can stimulate tumour formation, treatment can involve cutting nerve branches to the stomach. But this is invasive, so Timothy Wang of Columbia University, New York, and his team looked at blocking these signals using botox. They found that injections of the toxin can stop the growth of new tumours in mice with advanced gastric cancer (Science Translational Medicine, doi.org/vbs).

Wang now plans to test botox in people whose gastric tumours are resistant to chemotherapy.

This article appeared in print under the headline “Botox blitz for stomach cancer”

SEVERE pain? Reach for the yeast. Genetically engineered yeasts can now produce a range of opiates, including morphine. With growing anxieties about supplies of opium poppies, it could be just what the doctor ordered.

Christina Smolke of Stanford University in California and her colleagues have been looking at synthesising these complex molecules from simple sugars. In 2008, she genetically engineered yeasts to build an opiate precursor molecule. Now her team has finished the end of the pathway, engineering yeasts to synthesise finished drugs from another type of precursor molecule (Nature Chemical Biology, DOI&colon; 10.1038/nchembio.1613). “This work gets us very close,” says Smolke. All that’s left now, she says, is to combine the two phases in one strain of yeast, and fill in the missing steps.

IT’S a selfie that might save your sight. An implanted sensor could help people with glaucoma monitor the pressure in their eyes using a smartphone camera.

Glaucoma is the second-biggest cause of blindness after cataracts. It occurs when fluid builds up in the eye. This raises the pressure, damaging the optic nerve. Accurate pressure readings are crucial for giving the right treatment, but one-off measurements during check-ups produce variable results and can be misleading.

Yossi Mandel at Bar-Ilan University in Ramat Gan, Israel, and his colleagues have developed a pressure sensor which can be inserted into the eye during surgery to provide easy, regular monitoring from home (Nature Medicine, DOI&colon; 10.1038/nm.3621).

A few millimetres in length, the sensor can be embedded into the synthetic lenses used to replace the natural lenses of people with cataracts. It works like a miniature barometer, and contains a fluid column that rises with eye pressure. The level can be read at any time using a smartphone camera fitted with a special optical adapter. Software then analyses the image and calculates the reading.

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“Continuous monitoring is a clear unmet need in glaucoma,” says Francesca Cordeiro, a glaucoma researcher at University College London.

Mandel believes self-monitoring will lead to better treatment of the condition, and could enable people to skip unnecessary appointments when their eye pressures are on target.

This article appeared in print under the headline “Tiny implant turns smartphone into glaucoma monitor”

AS IF Australia’s spiders weren’t big and scary enough, it turns out denser, busier cities are allowing some of them to grow even bigger. The same thing could be happening the world over.

Elizabeth Lowe at the University of Sydney in New South Wales was surprised at just how large some harmless urban golden orb-weaver spiders (Nephila plumipes) were growing.

Examining more than 200 specimens around Sydney, Lowe and her colleagues found that the more concrete there was and the further they were from bushland, the bigger the spiders tended to be. Lowe says the spiders in bushland north of Sydney had an average mass of 0.5 grams. Those in an inner-city park near Bondi Beach averaged 1.6 grams (PLoS One, doi.org/vbf).

“It’s probably because of the urban heat-island effect and prey availability,” says Lowe. “Most invertebrates will grow to larger sizes if they are warmer. They are very sensitive to temperatures.”

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Healthy spider populations in cities should be celebrated, says Lowe&colon; they are mostly harmless to people, they eat pests and they are food for birds.

This article appeared in print under the headline “Spiders grow larger as cities swell”

But images captured by NASA’s Cassini spacecraft revealed steady vibrations at six different places in Saturn’s rings. Even though the rings are thousands of kilometres from Saturn’s surface, vibrations in them correspond to the way the planet squishes and contracts.

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Now Fuller has run a computer simulation of the vibrating rings. The results suggest that Saturn must have a stable, stratified layer, perhaps of liquid and rock, between the core and roiling exterior (Icarus, doi.org/vbh).

This is the first time a seismological investigation has been conducted on another planet. Future work should reveal more about the structure and evolution of gas giants.

This article appeared in print under the headline “To see inside Saturn, watch its rings”